In recent years, electrophotographic copiers and printers have gained popularity because of widespread office automation. With this background, there has been growing demand for electric power saving and downsizing of the machines in addition to high speed copying.
General formulations for toners in electrophotographic copiers and printers are shown in Table 1. One of the main factors for improving the fixability and offset preventing properties is a functioning agent, a component of the toner. Wax for use during the production of the toner, in particular, affects a binder resin, a principal constituent of the toner, and proves useful for improving the fixability, offset preventing properties and heat response characteristic.
That is, an electrophotographic copier or printer feeds a toner to a latent image on a latent image carrier to obtain a visible image, then transfers the resulting toner image to a plain paper or an OHP film, and fixes the transferred image. Currently, wide varieties of waxes are used in this field. Among them, low molecular weight polyethylene waxes and low molecular weight polypropylene waxes are in wide use. The current methods of producing polyethylene waxes and polypropylene waxes mainly employ Ziegler-Natta catalysts, and are classified into the polymerization process and the depolymerization process. However, waxes produced by these methods are defective in that the ratio of the weight average molecular weight Mw to the number average molecular weight Mn, the Mw/Mn ratio, exceeds 2, resulting in poor heat response characteristic. This adversely affects the fixability and offset preventing properties. Consequently, toners using such waxes cannot fully meet the social demand for saving in electric power and downsizing of the machines in addition to high speed copying.
TABLE 1 ______________________________________ (Unit: wt. %) Color- Charge Func- Mag- Electro- Binder ing control tioning netic lytic resin agent agent agent powder Solution Other ______________________________________ Two 50-100 0-20 0-10 0-20 -- -- -- com- ponent system One 0-100 0-20 0-10 0-20 0-60 com- ponent system ______________________________________
The present invention has been accomplished in the light of the aforementioned problems. The object of this invention is to provide a toner in a one-component developer and a two-component developer which toner leads to produce a higher grade copy image in an electrophotographic copier or printer, that is, the toner excellent in fixability, offset preventing properties and heat response characteristic.